Steel strip is customarily finished by rolling operations conducted in a number of rolling mills. Typically, the steel is rolled in a hot strip mill to a specified thickness and then sent to a cold mill for further reduction. The strip rolled in the hot mill normally is produced with a profile or crown, so that the strip is relatively thick at the center and progressively thins towards the edges. Those skilled in the art will understand that a continuous defect, or localized change in the profile, occurring in the hot mill could well have the effect of being carried through to the cold mill, thereby producing unusable product which already has the finishing cost built in.
The profile of a strip is a measure or indicator of the relative thickness achieved in the hot strip mill finishing operation. Monitoring of the profile is one means of assuring that the mill is satisfactorily producing steel strip of the required dimensional parameters. Numerous devices have been proposed for monitoring the strip profile, but these prior monitoring techniques have not been totally satisfactory. It should be noted that the occurrence of a single or point defect is relatively unimportant, whereas a continuous defect is of substantial importance because one or more strips may therefore be rendered unusable. The prior techniques have, to our knowledge, been more concerned with display of a single profile and detect, rather than through display of several profiles indicating a continuous detect.
In view of the above, it can be seen that there is a need for a method and apparatus permitting continuous defects to be detected through monitoring of the strip profile. Such a system should permit easy detection of continuous defects, either by the mill operator or, advantageously, through a computer analysis mechanism. The disclosed invention is just such a method and apparatus which is based upon three dimensional computer imaging utilizing data smoothing techniques applied to a finite number of strip profiles.